Currently available instruments used in analytical chemistry such as supercritical fluid extraction instruments automatically may generate multiple fractions from a single sample input and, with the incorporation of automation such as a robotic manipulator, a plurality of samples can be processed in a relatively automated fashion. However, there are several drawbacks to such a solution. First, the capital costs of the an lytical instrument and the robotic manipulator together are frequently so high as to negate any productivity gained by automation. Secondly, many instruments are not "robot-friendly" and the programming and customized hardware required to automate such systems can make them impractical. Finally, even in those systems where the samples can be input via a robotic manipulator, if the analysis performed is relatively simple, the speed at which the samples must be changed will exceed the speed at which the robotic manipulator can perform its tasks, reducing the productivity benefits to less than a maximum value.
It would therefore be desirable to automate sample input to an analytical instrument in a relatively inexpensive manner. Accordingly, it is an object of the present invention to provide a simple, reliable, accurate and robust system for automated sample input that can be integrated into an analytical instrument.
Additionally, many processes are performed upon samples at elevated temperatures, while others require cooling the sample. In the past, if multiple samples were formed in a queue, many or all of the samples were placed within a thermal zone to bring them to the appropriate temperature. For example, an entire tray of samples might be placed in an oven. Such procedures, however, are thought to have deleterious effects upon the samples or at least some of the constituents of interest in the samples, thereby diminishing the accuracy of any quantitative analysis performed. In other words, the thermal "cross-talk" between the samples results in a situation whereby different samples have different sample histories. Thus, in the case of biological samples, constituents such as metabolites in the last sample from a tray that has resided in an oven while other samples were analyzed might have been adversely affected as compared to the first sample taken from the tray at a time that may have been hours earlier. It is therefore another object of the present invention to provide methods and apparatus for handling a plurality of samples and moving a sample into and out of a thermal zone in a manner such that only one sample at a time is exposed to the thermal zone, thereby creating substantially the same sample history for each sample. Another (secondary) object of the present invention is to provide for a plurality of customized flow paths in an instrument that makes use of automatic zero (minimal) dead volume coupling, automatic thermal zone coupling, and selectable insertion.
As used herein, the term "instrument" refers to a wide variety of devices, including, but not limited to analytical instruments. Although sample preparation instruments such as supercritical fluid extraction instruments represent a preferred application of the present invention, the methods and apparatus disclosed herein are useful in other instruments such as supercritical fluid chromatographs, liquid chromatographs, and gas chromatographs, as well as other types of instruments, such as spectrometers or supercritical fluid extraction (SPE) instrumentation. Generally, the term "instrument" is meant to apply to both instruments that perform analysis and instruments that perform sample preparation steps prior to analysis, as well as instruments that process a sample for other reasons, such creating a refined material or extracting a material for other uses.